面向对象程序设计-C++ Type conversion (Static) & Inheritance & Composition【第十二次上课笔记】

这节课继续讲解了　static 作为静态数据成员　/　成员函数的用法

 

具体详解我都已注释出来了，大家可以慢慢看

有任何问题都可以在这篇文章下留言我会及时解答　:)

//static 静态数据成员

//static 静态成员函数



#include <iostream>



using namespace std;



class Integer {

public:

    int i;        

    static int number;            //Declaration,    整个类只有一个版本，所有对象共享

    //const static int number = 49;        在C++中也可以这样定义，不过比较奇葩

    int geti () { return i; }    //名称混编: _geti@Integer_    _v (Integer * const this)

    Integer (int k = 0) : i(42) { ++number; }

    static int getNumber ();    //名称混编: geti@Integer__v ()

};



int Integer::getNumber () {        //不需要写成static int Integer::getNumber

    //++i;    无法在静态成员函数中访问非静态成员

    //        非静态成员函数只能在静态成员函数中访问

    //this->i++;

    //        静态成员函数中无 this 指针

    return number;

}



int Integer::number = 0;//Definition



int main () {



    Integer Zhao, jin, wei, shi, tian, cai;

    

    Zhao.i = 78;

    Zhao.number = 4;



    cout << Zhao.i << endl;



    cout << Zhao.getNumber () << endl;

    cout << Integer::getNumber()<< endl;



    return 0;

}

 

以下是　组合　的例子

组合就是一个　has a 的关系，非常好理解

/*************************************************************************

    > File Name: Code05.cpp

    > Author: Jeremy Wu

    > Created Time: Mon 18 May 2015 10:47:03 AM CST

 ************************************************************************/



#include <iostream>

#include <string>



using namespace std;



//class Building;    //类的前置声明

//Building *bd;    //前置声明无法创建对象，但可以创建指针



class Building {



};



class Student {

public:

    int xuehao;

    double chengji;

    string address;

};



class Campus {    //relation : A Campus has Building & Student

    Building bd;

    Student st;

        

};



int main (){

    





    return 0;

}

然后着重介绍了继承的相关概念

继承就是一个　is -a 的关系

/*************************************************************************

    > File Name: Code06.cpp

    > Author: Jeremy Wu

    > Created Time: Mon 18 May 2015 10:55:00 AM CST

 ************************************************************************/



//构造函数调用顺序

//先调用基类构造函数

//再创建成员

//最后调用派生类构造函数



#include <iostream>

#include <string>



using namespace std;



class Person {                        //Base class

private:    

    string name, address;

    bool sex;

protected:                            //Protected, like private, but is avaiable in derived calss

    int age;

public:

    int getAge () { return age; }

    void setAge (int i) { age = i; }

    string getName () { return name; }

    void setName (string nm) { name = nm; }

    string getAdress () { return address; }

    void setAdress (string ar) { address = ar; }

    bool getSex () { return sex; }

    void setSex (bool sx) { sex = sx; }



    Person (string nm, string ar, int a, bool s) 

        : name (nm), address (ar), age (a), sex (s) {

            cout << "Person (string nm, string ar, int a, bool s) is called" << endl;

        }

    ~Person () { cout << "~Person () is called" << endl; }

};



class Test {

public:

    Test () { cout << "Test () is  called" << endl; }

    ~Test () { cout << "~Test () is called" << endl; }

};



class Student : private Person {        //Derived class

                                    //relation : A student is a person

                                    //if private derived, all the public funcions will be private as well as member varible

    //Person ps;

    Test t;

    unsigned int id;

public:

    int getId () { return id; }

    int setId (unsigned int id) { this->id = id; }

    

    void addAge () { ++age;    }

    //void addAge () { setAage (getAge () + 1 ); } //low efficiency



    Student (string nm, string ar, int a, bool s, unsigned int xh) 

        : Person (nm, ar, a, s), id (xh) {

            cout << "Student (string nm, string ar, int a, bool s, unsigned int xh) is called" << endl; 

        }

    ~Student () { cout << "~Student () is called" << endl; }



};

 

class UniversityStudent : public Student {

    //void print () { getName (); } 基类需要保护继承

};



void print (Person *p) {

    cout << p->getAge () << endl

        << p->getName () << endl

        << p->getAdress () << endl

        << p->getSex () << endl;

        //<< p->setId () << endl;    //Object slice 对象剪切

}



int main () {



    Person ps ("Zhao jinwei", "U.S.A", 20, true);

    Student st ("Ph.D Zhao", "CHINA", 20, false, 1322);



    //cout << st.getAge () << endl;

    st.addAge ();

    //ps.addAge ();

    cout << st.getName () << " " << st.getAge () << endl; //派生类对象继承了基类中成员

    print (&st); 



    return 0;

}